Dictation privacy system



April 29, 1969 L. E. EARLING DICTATION PRIVACY SYSTEM Filed Aug. 15, 1966 II F ,1 s mm fiaaaw .90 N.

INVENTOR. LEONARD E. EARLING lat M ATTORNEY United States Patent Office 3,441,686 DICTATION PRIVACY SYSTEM Leonard E. Earling, The Gray Manufacturing Co, Tecumseh, Mich. 49286 Filed Aug. 15, 1966, Ser. No. 572,523 Int. Cl. H04m 11/10 US. Cl. 179-100.1 11 Claims This invention relates to a dictation system wherein a recording station serves two or more dictating stations, and is particularly concerned with a privacy feature whereby only one dictating station can be operatively connected with the recording station at any one time.

Privacy circuits have been proposed in the past, seeking to achieve results similar to that contemplated by lhe present invention, but it is believed that the arrangement contemplated herein provides greater dependability, higher operating speed and greater simplicity than have been achieved for such purposes in the past.

It is among the objects of the present invention to provide a dictation system comprising a recording station including a voltage source having outer and intermediate terminals and a relay having a winding and contacts for connecting one of the outer terminals with the intermediate terminal; a dictating station including a gas tube, a resistor, a gating device having anode and cathode electrodes and a control element; the gas tube having an ionization voltage below that across the outer terminals and above that between one of the outer terminals and the intermediate terminal; the stations including a first series circuit comprising the voltage source, the winding, the gas tube and the resistor; a second series circuit comprising the voltage source, the winding, the gas tube, the control element, and one of the electrodes for firing the gating device; and a third series circuit comprising the voltage source, the winding and the electrodes; the third circuit energizing the winding to close the contacts and reduce the voltage across the gas tube to a value below its ionization voltage. The dictation system is primarily intended for installations including a plurality of similar dictating stations connected in parallel to the recording station. The dictation station includes a second relay winding in the third series circuit and also includes a microphone in the third series circuit. The voltage source preferably comprises a plurality of Zener diodes arranged in series. The dictation station includes a switch in the second series circuit, a resistor in the second series circuit and a switch in the third series circuit. The second series circuit includes the cathode electrode of the gating device, which preferably assumes the form of a silicon controlled rectifier.

A more complete understanding of the invention will follow from a description of the accompanying drawings wherein:

FIG. 1 is a circuit diagram depicting a dictating station interconnected with a recording station; and

FIG. 2 is a simplified circuit diagram depicting certain of the components of FIG. 1 and omitting other components, to facilitate an understanding of the principles contemplated by the invention.

The portion of the circuit of FIG. 1 representing the recording station is enclosed in broken lines and includes a DC supply 12 whose positive terminal 14 is connected by a conductor 16 containing a resistor 18 to an outer terminal 20 of a voltage source comprising Zener diodes 22, 24 and 26, the other outer terminal 28 of the voltage source being connected by a conductor 30 to the negative terminal 32 of the DC supply. The voltage source is also provided with an intermediate terminal 34, and connected across this intermediate terminal 34 and the outer terminal 20 are contacts 36 of a relay provided with 3,441,686 Patented Apr. 29, 1969 a winding 38. When the winding 38 is deenergized, the contacts 36 are open as depicted in FIG. 1. When the winding 38 is energized, the contacts 36 will be closed in manner to be described. One side of the winding 38 is connected to the outer terminal 20 by a conductor 40 and the other side of the winding 38 is connected by a conductor 42 to a resistor 44, switch contacts 46, and a conductor 48 to a terminal 50. The outer terminal 28 of the voltage source is connected by a conductor 52 to a resistor 54, and a conductor 56 to a terminal 58.

The dictating station, depicted outside of the broken lines of FIG. 1, has a conductor 60 connected to the terminal 50 and a conductor 62 connected to the terminal 58. When these conductors 60 and 62 are connected to their respective terminals 50 and 58, a voltage will be applied across the neon gas tube 64 above the ionization voltage of the tube to illuminate it and render it conducting. The path through which this circuit is completed is from the DC supply terminal 14, conductor 16, resistor 18, conductor 40, winding 38, conductor 42, contacts 46, conductor 48, terminal 50, conductor 60, neon tube 64, a conductor 66, a resistor 68, a conductor 70, conductor 62, terminal 58, conductor 56, resistor 54, conductor 52, conductor 30, and a negative terminal 32.

As soon as the neon tube 64 is illuminated, it will indicate to anyone at the dictating station that the recorder at the recording station 10 is available for use. Similarly, other dictating stations connected to the recording station in parallel will have similar neon tubes indicating to persons at those stations that the recorder at the recording station 10 is available for use. When a person at any one of the dictating stations removes the hand set from its cradle 72, movable contacts 74, 76 and 78 will assume the positions depicted in FIG. 1 to engage their upper contacts as shown. Now a circuit will be established starting at the positive terminal 14 of the DC supply through conductor 16, resistor 18, conductor 40, winding 38, conductor 42, resistor 44, contacts 46, conductor 48, terminal 50, conductor 60, neon tube 64, conductor 80, contacts 82 of a selector switch 84, resistor 86, contacts 74, conductor 88, gating element of a silicon controlled rectifier 92, cathode 94 of the silicon controlled rectifier, conductor 96, conductor 98, contacts of selector switch 84, conductor 62, terminal 58, conductor 56, reisistor 54, conductor 52, conductor 30, and to the negative terminal 32 of the DC supply 12. Completion of this second circuit serves to fire the silicon controlled rectifier 92 but due to the presence of the resistor 86, the current passing through the winding 38 has been insufficient to energize it to the degree necessary to close its contacts 36.

As soon as the silicon controlled rectifier 92 has thus been fired, a third circuit will be completed from the positive terminal 14 of the DC supply 12 to the conductor 16, resistor 18, conductor 40, winding 38, conductor 42, contacts 46, conductor 48, terminal 50, conductor 60, contacts 102 of selector switch 84, conductor 104, conductor 106, contacts 78 of the cradle switch, conductor 108, conductor 110, winding 112 of a second relay, conductor 114, conductor 116, resistor 118, conductor 120, microphone 122 of the hand set, conductor 124, conductor 126, resistor 128, conductor 130, anode 132 of the silicon controlled rectifier 92, cathode 94, conductor 96, conductor 98, contacts 100, conductor 62, terminal 58, conductor 56, resistor 54, conductor 52, conductor 30, back to the negative terminal 32 of the DC supply 12. Inasmuch as this third circuit does not contain the resistor 86, sufiicient current will flow to energize not only the Winding 38, but the winding 112 serving to close its contacts 134, 136 and 138 which serve to control circuits of the dictation system which are not directly involved in the privacy aspects of the system.

Inasmuch as completion of the circuit through the anode and cathode of the silicon controlled rectifier 132 passes enough current to energize the winding 38, its contacts 36 will be closed to shunt out the Zener diode 22 so that the voltage thereafter applied across the neon tube 64 will correspond with that across the outer terminal 28 and the intermediate terminal 34 which is substantially below the ionization voltage of the neon 64 so that it will no longer be ionized, and accordingly, will not glow and will not be conductive. The corresponding neon tubes of dictation stations connected in parallel will also be deionized so that they will not glow and will not conduct. Accordingly, after the circuit has been seized in the manner described, no other dictating station can establish connection with the recording station until after the hand set which had been removed to eifect seizure has been restored to its cradle.

The dictating station is also provided with a receiver 140, a start-stop switch 142 and various other switches and components. It will be noted that the selecting switch 84 is provided with three sets of terminals, adapting the dictating station to be connected to any of three recording stations, only one of which has been shown.

In the simplified circuit diagram of FIG. 2, most of the components not required for a description of the invention have been omitted, and a second, parallel connected dictating station 144 has been added. Inasmuch as reference numerals have been used in FIG. 2 corresponding with those of FIG. 1, no detailed description of FIG. 2 Will be required.

Whereas but one form of the invention has been described with reference to the accompanying drawing, those skilled in the art will recognize the variations contemplated within the scope of the appended claims.

I claim:

1. A dictation system comprising a recording station including a voltage source having outer and intermediate terminals and a relay having a winding and contacts for connecting one of said outer terminals with said intermediate terminals; a dictating station including a gas tube, a resistor, a gating device having anode and cathode electrodes and a control element, said gas tube having an ionization voltage below that across said outer terminals and above that between one of said outer terminals and said intermediate terminal; said stations including a first series circuit comprising said voltage source, said Winding, said gas tube and said resistor; a second series circuit comprising said voltage source, said winding, said gas tube, said control element, and one of said electrodes for firing said gating device; and a third series circuit comprising said voltage source, said winding and said electrodes; said third circuit energizing said winding to close said contacts and reduced the voltage across said gas tube to a value below its ionization voltage.

2. A dictation system according to claim 1 including a plurality of similar dictating stations connected in parallel to said recording station.

3. A dictation system according to claim 1 wherein said dictation station includes a second relay winding in said third series circuit.

4. A dictation system according to claim 1 wherein said dictation station includes a microphone in said third series circuit.

5. A dictation system according to claim 1 wherein said voltage source comprises a plurality of Zener diodes arranged in series.

6. A dictation system according to claim 1 wherein said dictation station includes a switch in said second series circuit.

7. A dictation system according to claim 1 wherein said dictation station includes a resistor in said second series circuit.

8. A dictation system according to claim 1 wherein said dictation station includes a switch in said third series circuit.

9. A dictation system according to claim 1 wherein said second series circuit includes said cathode electrode.

10. A dictation system according to claim 1 wherein said dictation station includes switching means for opening and closing said second and third series circuits.

11. A dictation system comprising a recording station including a voltage source; a dictating station including a gas tube, a resistor, and a gating device having anode and cathode electrodes and a control element; said stations including a first series circuit comprising said voltage source, said gas tube and said resistor, said first series circuit producing a voltage across said gas tube sufiicient to ionize said gas tube; a second series circuit comprising said voltage source, said gas tube, said control element, and one of said electrodes for firing said gating device; and a third series circuit of lower resistance than either of said first and second series circuits comprising said voltage source and said electrodes; energization of said third circuit reducing the voltage across said gas tube to a value below its ionization voltage.

References Cited UNITED STATES PATENTS 11/1966 Howard OTHER REFERENCES Boggs: Remote Dictating Selection Circuit, IBM Tech. Disclosure Bulletin, v. 7, No. 10, Mar. 1965, pp. 871-872. 

11. A DICTATION SYSTEM COMPRISING A RECORDING STATION INCLUDING A VOLTAGE SOURCE; A DICTATING STATION INCLUDING A GAS TUBE, A RESISTOR, AND A GATING DEVICE HAVING ANODE AND CATHODE ELECTRODES AND A CONTROL ELEMENT; SAID STATIONS INCLUDING A FIRST SERIES CIRCUIT COMPRISING SAID VOLTAGE SOURCE, SAID GAS TUBE AND SAID RESISTOR, SAID FIRST SERIES CIRCUIT PRODUCING A VOLTAGE ACROSS SAID GAS TUBE SUFFICIENT TO IONIZE SAID GAS TUBE; A SECOND SERIES CIRCUIT COMPRISING SAID VOLTAGE SOURCE, SAID GAS TUBE, SAID CONTROL ELEMENT, AND ONE OF SAID ELECTRODES FOR FIRING SAID GATING DEVICE; AND A THIRD SERIES CIRCUIT OF LOWER RESISTANCE THAN EITHER OF SAID FIRST AND SECOND SERIES CIRCUITS COMPRISING SAID VOLTAGE SOURCE AND SAID ELECTRODES; ENERGIZATION OF SAID THIRD CIRCUIT REDUCING THE VOLTAGE ACROSS SAID GAS TUBE TO A VALUE BELOW ITS IONIZATION VOLTAGE. 